Utility knives of diverse shapes and sizes are common to virtually all of the construction, repair, and craftsmanship trades. Typically, a utility knife consists of a handle which holds a replaceable, presharpened blade in an operative position. Both the handle and the blade can be manufactured in various shapes and configurations designed to meet the particular needs of different manufacturing and repair tasks. Generally, utility knife blades are a presharpened, disposable item. In practice, the user of the knife removes and discards an old blade and replaces it with a new one when the user deems that the old blade is broken or has lost an appropriate degree of sharpness. Often, utility knife blades are prepared with two opposing points so that the blade can be reversed when the first point dulls, effectively doubling blade life.
Many different styles of utility knife handles are available to the user. The handle style is selected to provide features which will fully enable the operator to perform a specific task. For example, short utility knife handles of approximately six inches in length hold the operative blade in a position near the user's thumb and forefinger. This blade positioning facilitates a great deal of control over the blade which is useful for tasks which require precision, the cutting of small openings in a drywall panel, for example.
A second type of short handled utility knife also positions the operative blade near a user's thumb and forefinger, facilitating control, but angles the blade downward and away from the user's thumb. This type of handle and blade configuration has been found useful for tasks which require a long, pulling type cut such as the trimming of carpet.
Short handled utility knives such as those described above are found lacking by users who desire to trim away the sealant which holds an automobile windshield in place. The sealant, typically a silicone or urethane type adhesive, is applied to the interior perimeter of the windshield, the interior being defined with respect to the passenger compartment of an automobile or truck. Upon installation, the windshield mates with a special flange formed in the body or frame of an automobile or truck and the sealant both bonds the windshield to the automobile frame and provides a wind and watertight seal. In the event a windshield is broken by a road hazard and must be replaced, the sealant must be cut between the automobile frame and the windshield to allow the removal of the broken windshield.
The procedure of cutting the windshield sealant is made difficult because most modern automobiles utilize a steeply sloped windshield, therefore, the angular workspace between the windshield and the upper portion of the dashboard on the interior of the vehicle can be quite narrow. Often, the space between the windshield and the top of the interior dashboard is so restricted that a knife user could not fit both their hand and a short handled utility knife into the space necessary to accomplish the cut. In addition, many short handled utility knives are manufactured with a ridged thumb button for blade extension and a large machine screw which mates the handle sides. These protuberances from the handle can scratch or otherwise mar the upper surface of an automobile dashboard or other work surface.
In response to the difficulty presented by the restricted work space, and in order to avoid the risk of marring a dashboard finish, long handled, narrow throated utility knives have been developed. This type of utility knife is commonly known as a “long knife.”
The extended, narrow throat of a long knife allows an operator to access and cut a windshield seal without requiring their hand to be placed in the narrow area immediately between the upper side of the automobile dashboard and the inside of the bottom of the windshield. In addition, a long knife ideally has no screws, thumb buttons, or other protuberances from the gently curved handle, therefore, the risk of scratching or marring the finish of the upper side of an automobile dashboard during the sealant cutout operation is minimized.
Long knives have also found acceptance in the masonry, roofing, plumbing, and pruning trades, where the extended, narrow throat of the tool provides a distinct advantage over a standard, short handled utility knife for applications such as removing caulk from masonry expansion joints, cutting the seal around a bathtub, sink, or toilet, or trimming cacti. In addition, the extended length of the handle utilized in a long knife allows an operator to safely place two hands on the handle for applications where a great deal of operator pressure may be applied to the blade.
Certain long knives are configured to be used with the most commonly available type of utility knife blade: one which is substantially trapezoidal in shape with dual mounting indentations formed in a mounting edge opposite the cutting edge. One prior art long knife features a throat which defines a blade slot which is pierced by a transverse mounting post situated near the top of the blade slot. In use, an operator inserts a standard utility knife blade into the blade slot and positions one of the mounting indentations over the transverse mounting post. The rear portion of the utility knife blade abuts a lower wall of the blade slot opposite the mounting post so the blade is more or less securely held in the slot so long as the blade point is pressed down into a cutting material and drawn toward the operator during cutting operations.
This type of long knife advantageously allows an operator to easily replace blades without the use of tools. Blade removal is accomplished by grasping the point of the blade, pulling the blade away from the mounting post, and removing the blade from the blade slot. Easy blade replacement is desirable because utility knife blades, often break or become dull. Relatively quick and tool-free blade replacement can increase operator productivity.
Prior art long knives featuring a single mounting post and configured to be used with standard utility knife blades do not hold a blade securely in all circumstances. For example, if the top side of the blade is bumped or a cutting motion other than a draw toward the operator is employed, the mounting indentation of the blade may be knocked loose from the mounting post, allowing the blade to fall out of the blade slot.
Other prior art long knives feature a general configuration similar to that described above, however, separate locking mechanisms are utilized to secure a blade. Typically, the locking mechanisms are a simple plate and screw structure. Such locking mechanisms securely hold a utility knife blade, however, the ability to quickly change a blade without the use of tools is lost. Thus, prior art long knives either feature a blade holding mechanism which securely holds a blade under all circumstances, or a mechanism which allows for the quick removal and replacement of a blade without the use of tools which may not hold a blade securely under all circumstances.
The present invention is directed toward overcoming one or more of the problems discussed above.